1. Field of the Invention.
This invention relates, generally, to improved methods for wound management using an external wound dressing composition or admixture containing trehalose in combination with adhesives that adhere to wet and dry skin and hydrophilic absorbents. Such compositions uniquely protect living cells and proteins in the wound fluid from desiccation when available water is reduced or removed.
2. Description of Related Art.
As the understanding of the healing process has progressed, various theories have been advanced regarding the most advantageous ways to protect wounds and to optimize the healing process. For many years, absorptive wound dressings, such as a gauze, were used because it was generally believed that wounds required air drying or desiccation to promote epithelial resurfacing without infection. Subsequently, however, it was found that moist conditions were preferable to a dry wound condition for the promotion of healing. Recently, studies have shown that it is preferable to maintain a fluid environment over the wound site in order to promote optimum wound healing. No increase in infection has been associated with wet wound healing.
To provide a device that enhances wound healing is challenging in that wounds are not uniform. Wounds actually have three different areas to consider where wound management is concerned. The first area is the surrounding intact skin. This area is used to fix and adhere the device over the open wound bed. This is where the combination of adhesives that adhere to dry and wet skin must provide adequate skin adhesion, yet be non-adhering to the wound bed. Dressings are commercially available that do this very well and, as such, meet the specific requirement. The second area of concern is the wet wound bed. This area initially will be extremely wet during the inflammatory stage of wound healing and challenge the dressing device to absorb copious amounts of fluid. Again, commercially available dressings contain absorbents, and super absorbents that meet this need. But the problem is that they can absorb too much fluid and dry out the wound bed. This then brings us to the third area of concern, which is the regenerating tissue layer. It is critical that for optimal wound healing to occur, this area must be moist enough for new cells to be adequately supplied with nutrients. If this area becomes dry, then these fragile regenerating cells will die, and the wound healing process will cease. The inclusion of trehalose in wound healing devices is unique in that trehalose will substitutionally bind to cellular proteins, replacing water molecules, thereby protecting them from dehydration during the dehydration process. Trehalose is also selectively effective in the three environments detailed above since its large molecular structure, relative to water, precludes absorption and remains in the wound available as a water substitute.
Other factors must be considered in the development of wound dressings which provide a fluid environment over the wound site. For example, wound dressings must be easily stored and sterilized. Further, wound dressings should be at least toxicologically unobjectionable and be as biocompatible as possible with the human body. Other considerations in the development of wound dressings include sufficient gas permeability for ventilation of vapors from the wound and surrounding skin area; non-adherence to the regenerating tissue of the wound, a high degree of absorbability for wound exudate, bacteria, and necrotic cell material; and as previously stated, the dressing must be conducive to promoting granulation tissue or re-epithelization necessary to provide new skin growth.
It is important to strike a balance between all of these competing factors in the development of wound dressings which promote wound healing. Of particular importance is the balance between a dressing's ability to absorb wound exudate and simultaneously maintain the moisture needed at the wound regrowth site to promote wound healing. Improper moisture maintenance at the wound site can deleteriously effect the healing process. For example, many wound dressings, if allowed to dry over a wound site may stick to the wound. When the stuck dressing is removed from the wound, damage to the integrity of the reepithelized tissue at the wound site may result. Further, if a wound is allowed to dry out due to inadequate coverage by a dressing, the healing process is compromised and reepithelized tissue may dry out and die. It then becomes necessary to remove the dead tissue and again attempt to regain a moist healing environment at the wound site. It has proven particularly difficult to maintain a moist environment at the wound site when the nature of the wound necessitates a wound management protocol that requires frequent dressing changes. This is especially true during the first stages of healing process where there is a high degree of wound exudate and the new dressings have a high initial uptake of liquid.
In an attempt to facilitate wound healing, different dressings and wound management regimes have been developed. Wound management regimes have utilized many materials including gauze, tapes, film dressings, hydrocolloids, gels, foams and saline solutions or other pharmaceutically acceptable carriers in an attempt to promote wound healing. Numerous approaches, having varying degrees of success, have attempted to overcome the deficiencies in the prior art wound dressings which would promote healing. Specifically, various saccharide containing wound dressings have been developed which exhibit excellent moisture absorption capabilities. In addition, saccharides have other beneficial characteristics, such as film forming capabilities, bactericidal effectiveness and they may act as sources of energy. For example, U.S. Pat. No. 4,929,577 to Cornell, U.S. Pat. No. 4,883,478 to Lerailler et al., U.S. Pat. No. 4,788,237 to Le-Khac, U.S. Pat. No. 4,664,105 to Dautzenberg et al., U.S. Pat. No. 4,556,056 to Fischer et al., U.S. Pat. Nos. 4,307,717 and 4,306,551 to Hymes et al. and U.S. Pat. No. 2,137,169 to Levey disclose various saccharide containing wound dressings.
However, in all of these dressings it has proven difficult to strike a balance between their excellent and copious moisture absorption capabilities and the need to maintain enough moisture at the wound regrowth site for the promotion of the healing process, particularly when a fresh dressing is applied. Problematically, these dressings can absorb too much moisture initially, which subsequently causes dehydration of the wound site and loss of structural integrity of cells and protein constituents of the healing wound bed.
In view of the prior art at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how a dressing could simultaneously absorb wound fluid and not damage cells and delicate proteins by excessively removing wound fluid from the wound site.